Lubricating oil and lubrication therewith



Patented Sept. 3, 1940 LUBRICATING OIL AND LUBEICATION THEREWITH Elmer William Cook, New York, N. Y., assignor to Tide Water Associated Oil Company, Bayonne, N. J a corporation of Delaware No Drawing. Application July 6,1938,

. Serial No. 217,718

10 Claims. -(01. 252-53) This invention relates to mineral oil compositions comprising petroleum oils of a viscous or lubricating nature as contrasted with non-viscous hydrocarbons of the-character of gasoline or kerosene. It is particularly concerned with mineral oil compositions comprising lubricating and like oils having incorporated therewith small but suftion is concerned with lubricants intended for service in the lubrication of internal combustion engines. These now are frequently equipped with bearings comprising or surfaced with cadmiumsilver, cadmium-nickel, copper-lead or like alloys having substantially the corrosion susceptibility of the stated alloys. Such harder, higher melting alloys are in certain respects better adaptedto the requirements of modern internal combustion engines than the conventional Babbitt metal bearings, in view of greatly increased bearing pressures and the high temperatures whichmay obtain at bearing surfaces during operation. The mechanical superiority of cadmium-silver and other special alloy bearings is largely ofiset, however, by a marked susceptibility to corrosion under service conditions by many available lubricating oils-particularly-oils which by nature or refining are of the character generally regarded as superiorlubricants by conventional criteria (e. g., high viscosity index, substantially or reasonably free from sludge-forming tendencies, etc.)

Under service conditions the presence of cadmium-silver and like alloys appears to catalyze reactions tending toward lubricant degradation. Such alloys likewise seem to be particularly-susceptible to corrosion by lubricants which have undergone deterioration in service. It has been suggested that corrosion of bearing metals in in-' plain causes or results. It has been found that organic arsenites including both alkyl and aryl derivatives comprise a class providing compounds efi-ective'to inhibit oil deterioration and deterioration effects. According to the invention, service degradation of oils is retarded and the corrosiveness of motor oils to cadmium-silver and like alloys markedly diminished by dissolving in the oil prior to use small but suflicient proportions of an organic arsenite inhibitor. It is, therefore,- an object of the invention to improve, and to prepare improved, lubricating oils of petroleum origin by incorporating therein an organic arsenite inhibitor in small but effective proportions.

In a special aspect, the invention may be regarding as encompassing a novel method of lubrieating bearings surfaced with an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel or copper-lead alloys by applying to the bearing surfaces lubricant comprising mineral hydrocarbon oil normally tending to corrode such 'alloys and having incorporated therein corrosio" retarding proportions of an organic arsenite inhibitor.

Inhibitors according to the invention are compounds conforming to the general formula R-O wherein the R's designate organic radicals such as hydrocarbon residues which may be aryl or alkyl, or may be substituted aryl or alkyl groups. Among the alkyl arsenites, those having from 4 to about 10 carbon atoms in the alkyl residues are presently preferred and the aliphatic chain may be either straight or branched. The preferred aryl arsenite inhibitors according to the invention are the phenyl and cresyl arsenites in view of the greater solubility of these compounds as compared with the higher molecular weight aryl arsenites. The invention also embraces arsenites in which the organic radical is an alicyclic hydrocarbon residue of aliphatic character as in the case of tricyclo-hexyl arsenite. The hydrocarbon radicals in both alkyl and aryl arsenites may be substituted at one or more carbon atoms by such groups as alkyl, aryl, aralkyl, alkoxy, amino, hydroxy, and nitro radicals. Inhibitors selected from the defined class need not consist solely of one or another pure organic arsenite, mixtures being effective. This is a beneficial aspect of the invention, since the synthesis of a given arsenite frequently is accompanied by the by-product formation of small amounts of a related compound (e. g.

some tri-ortho cresyl arsenite maybe formed in the synthesis of tri-para cresyl arsenite) i In such cases it is unnecessary to carry refinement of the reaction p roduct to the point pf isolating an absolutely pure compound.

Various methods are described in the literature for the synthesis of organic arsenites; In most cases I have found it convenient to employ the simple reaction of tri-oxide of arsenic (A5202) and an appropriate alcohol or hydroxy-aromatic compound with the aid of heat. Water is evolved during the reaction and is continuously removed as steam, heating being continued until all water has been driven ofi. The reaction mixture then is cooled, anhydrous benzene added, and any residual unreacted ,tri oxide of arsenic removed by pected, some being more efiectivel than others ingiven proportions. In general it is preferred to use those having greatest inhibitor eifectiveness at small concentrations.

As'indic'ated hereinbefore, organic arsenite in-.

filtration. The benzene diluent and residual unreacted alcohol are readily removed fromthe filtrate by distillationunder reduced pressure. The

organic arsenite product may be refined to de-. sired extent by' conventional methods.

Using the foregoing general method of syntheate reagent, the product in this instance being a' colorless, mobile liquid boiling at about 150 C. at

10 mm. mercury. 7 To produce tri-cresyl arsenites, an appropriate cresol is used," the product in the case of tri-para cresyl arsenite, for example, being a viscous, yellow liquid. In the-case of naphthyl arsenites a suitable naphthol, for example, betanaphthol, is reacted withtri-oxide of arsenic.

Tri-butyl arsenites may be prepared with the aid of butyl or iso-butyl alcohol and colorlessliquid products are obtained, the iso compound, for

example, boiling at'24'2. C. under normal atmospheric pressure. Tri-cyclo-hexyl' arsenite is produced by the reaction of cyclo-hexyl alcohol with tri-oxide ofarsenic; and similarly for other alkyl or aryl arsenites 'which comprise efltective inhibi- 7,

tom according to the invention.

The individual eifectiveness of organic arsenite inhibitors will vary somewhat as might be exhibitors have proved markedly efiective in retarding the corrosion of-bearing metals by lubricating, oils normally corrosive thereto under high temperature service. conditions obtaining in internal combustion engines. Concurrent oil-deterioration as evidencedby undesirable-increasa in viscosity, carbon residue, neutralization number and Indiana preciptiation number also is retarded in beneficial degree by the use of inhibitors as herein disclosed. Generally, the circumstances giving rise to the 'need for inhibitors in motor 'oil serv ice, particularly the problem of bearing corrosion,

include high operating temperatures, for ex-, ample 300 F.-400 F. or even higher in certain localized areas. The present invention'provides an. adequate over-all improvement in lubricants and in lubrication for such service.

The. utility of organic arsenite, inhibitors extends'likewise to lubrication with mineral oilsunder service conditions involving lower operating temperatures. By way of further illustration may be mentioned in particular the value of such inhibitorsin turbine oil In such use, the

oil temperature is relatively low, as compared.

with temperatures encountered in high speed in- .ternal combustion engines, but contacted metal surfaces may catalyze acid or sludge formation in the lubricant with eventual emulsification due to the presence of water. Inhibitors according to the invention serve eificiently in retarding oil deterioration under such service conditions.

Thus it willbe seen that'the invention supplies inhibitors of broad utilityin mineral oil environment. Mineral oils of lubricating viscosity-are definitely improved for a wide range of services by the addition thereto of an organic arsenite inhibitor'in small but sufficient proportions to.

retard oil deterioration and deterioration efiects.

The proportion of an organic arsenite inhibitor necessary to accomplish the objects of the present invention is quite small, percentages of the order of 0.05 %-0.2% by'weight or even less dissolved in mineral lubricating oil exhibiting a marked inhibiting effect. Larger proportions within the limit of solubility for a given arsenite may be used if desired but the smaller proportions ordinarily are wholly sufiicient and, in the interestsof economy, preferable. In the illustrative tests reported hereinafter certain specific proportions of inhibitor were used,.but stated percentages herein are not intended as a limitation upon the contemplated scope and practice of the invention. The inhibitors may be, and are intended to be, em ployed, in any inhibiting proportion.

The tendency of motor oils to corrode bearing metals may be determined by a convenient test which affords a ready method of obtaining a comparative evaluation of motor oils in the laboratory. In this test method a group of bearings,

ordinarily including at least one each of several of the newer bearing metal alloys (viz: cadmiumsilver, cadmium-nickel and-copper-lead) is supported in a chamber in which air may circulate and the bearing surfaces are exposed for a. period of 22 hours to a stream of oil sprayed under pressure continuously upon the corrodible area. The

oil is maintained at a temperature of approxi-' mately 335 F. and the spray is so directed as to disperse the oil over the surfaces of the bearings. Means are provided for recirculating the sprayed oil so that a given quantity is used for a given test, thus simulating service conditions in an engine.

The measure of corrosion is taken as the loss in weight of the bearing per unit of exposed corrod- I ible surface. Concurrent oil deterioration is determined by tests on the used oil after-a,,given supplied by the Scientific Instrument Company of The test method described ,above is carried out in the familiar Underwood corrosion apparatus.

Detroit, Michigan, in accordance with General Motors specifications.

- Results obtained'utilizing the foregoing test for comparative'evaluation ofv 'motor oils with and without an inhibitor according to the invention provide specific illustration of the value and inhibiting effectiveness of triphenyl arsenite. The

oil used for the test was an S. A. E. 20 motor oil j comprising a blend of well refined paramnic base stocks and having an A. P. I. gravity of 30.1, 'Sayin an amount of 0.2% by weight based on the oil.

During each run cadmium-silver, cadmium-nickel and copper-lead bearings all were present; and,

comparative losses in weight per square decimeter I due to corrosion were observed as follows for the respective bearings:

Eagample A B t ll l caring rip eny Blank arsenite Gram Grams Cadmium-silver. 6. 6 0. l Cadmium-nickel 5.2 0.6 Copper-lead. 0. 9 0.07

Example .8

Oil plus Oil Bearing tri-p-cresyl blank arsenite Grams Grams Cadmium-silver. 5. 1 0. 6 Cadmium-nlckeL 9. 0 l. 8 Copper-lead 3.0 0. 2

Example C Oil plus Oil Bearing tri-isoarnyl blank arsenite Cadmium-silver No loss. Cadmium-nickel.-- Do. Copper-lead Do.

The used 011 tests in Example A were as follows:

Oil Oil lus blank inhi itor A. P. I. gravity 23.1 27. 0 Saybolt vis. 100 F. 727 470 Saybolt vis. 210 F- 77 64 Carbon residue 3. 60 1. Neutralization No 5. 65 3. 41 Indiana. precipitation No 13. 0 ll. 0

In Example B the used on had the following comparative tests:

blank inhi ltor A. P. I. gravity 19.1 26. l Saybolt vis'. F 3266 5% Saybolt vis. 210 F. 151 69 Carbon residue 3. 72 2. 30 Neutralization No 12. 0 3. 36 Indiana precipitat on 'll'o 23 7 The used oils in Example C had the following tests:

Oil Oil lns blank inhi itor A. P. I. gravity l9. 1 28.4 Saybolt vis. 100 F. 3266 387 Saybolt vis. 210? F 151 .60 Carbon residue. J. 72 l. 22 Neutralization No. 12.0 1.18 Indiana precipitation No 23' 6 ported above.

'rosive deterioration of bearing metal alloys invention provides efllciently improved lubrication for internal combustion engines, particularly those equipped with bearings of the cadmium-silver type. Ordinarily the oil selected for use, in

applying the lubricating method of the invention to its intended service, will be of a character generally regarded as of superior grade and refining, i. e., of the low sludge forming or relatively sludge-resistant type as evaluated by conventional tests such as the Indiana oxidation test. Thus, the invention finds particular utility 'in making possible beneficial use of such oils in internal combustion service by avoiding deleterious consequences otherwise encountered when no preventive measures are taken against the coras herelnbefore referred to. By another test method, which has proved of particular convenience inpalthough not limited to, the evaluation of oilsintended for such service as the lubrication of steam turbines, the broad range of effectiveness characterizing organic arsenite inhibitors may be further demonstrated. In this test the deterioration of mineral lubricating oil under relatively low temperature service conditions is accelerated in marked degree, thereby making it possible to compare the relative tendencies toward deterioration of various oilswith and without inhibitors. A measured quantity of oil and water (ordinarily 300 cc. of oil and 30 cc. of distilled water) is placed in a small closed brass chamber or capsule, in which an air pressure of 50#/sq. in. is maintained, and subjected to violent agitation for a test period of hours with the chamber immersed during the test period in a steam bath maintained at approximately 212? F. Air in the chamber is changed at 24 hour intervals to insure a sumciency of oxygen throughout the test period. The neutralization number (milligrams KOH equivalent per gram of oil) of the oil layer at the ed of. the test period is taken as the measure of deterioration.

I Example D 150 Saybolt seconds, an iodine number of about 10, and a color of about 1 A. S, T. M. -The following comparative results were obtained:

- Neutralization Inhibitor No. of oil layer alter test N one (average value of several runs) 0. 21 0.05% tri-phenylarsenite 0. 08

It will be clear, therefore, that the i The data tabulated above show clearly the effectiveness of an inhibitoraccording to the invention in retarding the deterioration of a well refined medium viscosity mineral oil of a character adapted to steam turbine lubrication service.

It will be understood, of course, that all of the foregoing examples are given by way of illustration and not by way of limitation; the use of an inhibitor according to the invention, in other than the specific proportions mentioned and in other than the specifically designated oils,

being within the contemplated scope thereof.

I claim:

1. Method o'f lubricatlng bearing surfaces, at least one of 'which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copper-lead alloys, whichcomprises applying to the bearing surfaces lubricant having incorporated therein 'a sufficiently oil-soluble alkyl arsenite in corrosion inhibiting proportions.

2. Method of lubricating bearing surfaces, at least. one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copper-lead a1-' loys, which. comprises applying to the bearing" surfaces lubricant having incorporated therein corrosion inhibiting proportions of a tri;amyl arsenite.

3. Method of lubricating bearing surfaces, at

least one of which comprises an alloy having substantially the corrosion susceptibility of cad-.-

mium-silve'r; cadmium-nickel and copper-lead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein corrosion inhibiting proportions of a tri-butyl.

arsenite.

4. Method of lubricating bearing surfaces, at least one, of .which comprises an alloy having substantially the :corrosion susceptibility of oadrmum-silver, cadmium-nickel and copper-lead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein corrosioninhibiting proportions of tri-iso-amyl aresnite.

5. Method of lubricating bearing surfaces, at"

least one'of which comprises an alloy having substantially .the corrosion susceptibility of cad-' mium-silver, cadmium-nickel and copper-lead alloy s, which comprises applying to the bearing surfaces lubricant having incorporated therein corrosion inhibiting proportionsof tri-iso-butyl containing a. tri-amyl arsenite in a small but suflicient amount to inhibit said deterioration.

8. Mineral oil composition suitable for internal combustion engine and steam turbine lubrication comprising a relatively heavy, viscous lubricating oil normally subject to deteriation in service containing a tri-butyl arsenite in a small but sufficient amount to inhibit said deterioration.

9. Mineral oil composition suitable for internal combustion engine and steam turbine lubrication comprising a relatively heavy, viscous lubricating oil normally subject to deterioration in service containing tri-iso-amyl arsenite in a small but sufficient amount to inhibit said deterioration;

10. Mineral oil composition. suitable for in-* temal combustion engine and steam turbine lubrication comprising a relatively heavy, viscous lubricating oil normally subject to deterioration in service containingtri-iso-butgl arsenite in a small but sufficient amount to inhibitsaid de- 85 terioration. ELlVIER WILLIAM COOK.- 

